METHOD FOR FABRICATING ELECTRONIC COMPONENT

Abstract

A method for fabricating an electronic component includes the steps of: forming a base material layer of, for example, nickel on a base material of copper, copper alloy, aluminium, or aluminium alloy; applying, as a catalyst, one or more metals selected from the group consisting of gold, palladium, platinum, silver, rhodium, cobalt, tin, copper, iridium, osmium, and ruthenium, on the base material layer; and forming a surface layer by an electroless tin plating bath including trivalent titanium as an reducing agent and pyrophosphate salt as a complexing agent. The surface layer has a thickness of 0.5 μm or more.

Claims

1. A method for fabricating an electronic component, the method comprising: a base material layer formation step of forming a base material layer of nickel or a nickel alloy by an electroless nickel plating bath or an electroless nickel alloy plating bath on a substrate of copper, a copper alloy, aluminium, or an aluminium alloy; a catalyst application step of applying, as a catalyst, one or more metals selected from the group consisting of gold, palladium, platinum, silver, rhodium, cobalt, tin, copper, iridium, osmium, and ruthenium, on the base material layer, and a surface layer formation step of forming a surface layer by an electroless tin plating bath or an electroless tin alloy plating bath containing trivalent titanium as a reducing agent and pyrophosphate salt as a complexing agent, wherein, in the surface layer formation step, a surface layer with a thickness of 0.5 μm or more is formed.

2. The method according to claim 1, wherein the electroless tin plating bath or the electroless tin alloy plating bath includes nitrogen-free organic thiol.

3. The method according to claim 1, wherein the electroless tin plating bath or the electroless tin alloy plating bath includes sulfur oxoacid.

4. The method according to claim 1, further comprising: a titanium reduction step of reducing tetravalent titanium generated in the electroless tin plating bath or the electroless tin alloy plating bath in the surface layer formation step, to trivalent titanium by electrolization, wherein: in the titanium reduction step, in a reduction process tank including an anode chamber and a cathode chamber partitioned by a cation exchange membrane, a part of a plating solution in a plating tank where the step of forming the surface layer is performed is moved to the cathode chamber, and the surface layer formation step and the titanium reduction step are performed in parallel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a cross-sectional view illustrating stacked films according to one embodiment.

[0011] FIG. 2 is a schematic view illustrating an example of an electroreduction tank.

DESCRIPTION OF EMBODIMENTS

[0012] In a method for fabricating an electronic component according to this embodiment, stacked films 102 including a base material layer 121, a catalyst 122, and a surface layer 123 formed on a base material 101 as illustrated in FIG. 1.

[0013] The base material 101 may be, for example, an interconnection layer or a connection pad formed on the surface a printed wiring board, a semiconductor wire, or other components. The base material 101 may also be, for example, a metal layer formed by plating, spattering or other processes on the surface of an interconnection layer, a connection pad, or other materials. The base material 101 may be a layer of, for example, copper (Cu), aluminium (Al), or an alloy of copper or aluminium. A copper alloy or an aluminium alloy may include, as an alloy component, nickel, chromium, manganese, iron, cobalt, tungsten, titanium, and/or silicon, in addition to copper or aluminium. The content of the alloy component is preferably 50% or less, and more preferably 10% or less. The thickness of the base material 101 is not specifically limited, and is preferably 0.05 μm or more, more preferably 0.1 μm or more, preferably 100 μm or less, and more preferably 60 μm or less.

[0014] The base material layer 121 can be a layer of nickel(Ni) or a nickel alloy including for example, phosphorus or boron as an alloy component. The content of the alloy component in the base material layer 121 is preferably 50% or less, and more preferably 15% or less. In particular, a nickel-phosphorus layer including phosphorus is preferable because of easiness in forming a good film. The thickness of the base material layer 121 is not specifically limited, and from the viewpoint of connection reliability, is preferably 0.05 μm or more, more preferably 0.1 μm or more, preferably 15 μm or less, and more preferably 7 μm or less.

[0015] The catalyst 122 can be one or more metals selected from the group consisting of gold (Au), palladium (Pd), platinum (Pt), silver (Ag), rhodium (Rh), cobalt (Co), tin (Sn), copper (Cu), iridium (Ir), osmium (Os), and ruthenium (Ru). Among these metals, gold, palladium, platinum, silver, and rhodium are preferable because of high catalyst effects and easiness in application. As illustrated in FIG. 1, the catalyst 122 can be formed in a layer pattern covering the entire surface of the base material layer 121. Alternatively, the catalyst 122 does not need to cover the entire surface of the base material layer 121, and may be applied in an island shape or a net shape in which part of the surface of the base material layer 121 is exposed. The thickness of a portion coated with the catalyst is not specifically limited, and from the viewpoint of forming a good surface layer 123, is preferably 0.0001 μm or more, more preferably 0.001 μm or more, and preferably 0.1 μm or less.

[0016] The surface layer 123 can be a layer of tin(Sn) or a tin alloy. From the viewpoint of connection reliability, the thickness of the surface layer 123 is 0.5 μm or more, and preferably 1.0 μm or more. The upper limit of the thickness is preferably 15 μm or less, and more preferably 10 μm or less, from the viewpoint of, for example, a film formation time. The tin alloy can include, for example, silver (Ag), copper (Cu), bismuth (Bi), or nickel (Ni), other than tin, as an alloy component. Specific examples of the tin alloy include Sn—Ag, Sn—Ag—Cu, Sn—Cu, Sn—Bi, Sn—Cu—Ni, and Sn—Cu—Bi.

[0017] The stacked films 102 according to this embodiment are formed in the following manner. After the surface of the base material 101 is subjected to treatments such as degreasing, soft etching, and pickling, the base material layer 121 is formed by using electroless nickel plating or electroless nickel alloy plating (hereinafter collectively referred to as electroless nickel platings). In a case where the base material 101 is made of, for example, copper, it is sufficient to apply a catalyst before the electroless nickel platings are performed. The catalyst can be, for example, palladium (Pd), silver (Ag), gold (Au) or platinum (Pt). In the case where the base material 101 is made of, for example, aluminium, the electroless nickel platings can be performed after a zincate process.

[0018] Then, the catalyst 122 is applied to the surface of the base material layer 121. The catalyst 122 can be applied by immersing the base material in a solution containing a salt of a potentially noble metal, for example. The catalyst application can be performed by physically adsorbing a colloidal catalytic metal onto the surface of the base material layer 121.

[0019] The surface layer 123 is formed by using an electroless tin plating bath on the base material layer 121 to which the catalyst 122 is applied. The electroless tin plating bath includes a tin compound, trivalent titanium as a reducing agent, and pyrophosphate salt as a complexing agent.

[0020] The tin compound may be any compound that produces divalent tin ions in the plating bath. Examples of the tin compound include tin(II) chloride, tin(II) sulfate, tin(II) pyrophosphate, tin(II) bromide, tin iodide(II), tin(II) fluoride, and tin(II) phosphate. Although the concentration of the tin compound in the plating bath is not specifically limited, and from the viewpoints of, for example, film quality and a precipitation rate, the tin concentration is preferably 0.1 g/L or more, more preferably 1 g/L or more, preferably 30 g/L or less, and more preferably 15 g/L or less.

[0021] Trivalent titanium as a reducing agent can be, for example, trivalent halogenated titanium or titanium sulfate, and can be titanium(III) chloride, titanium(III) bromide, titanium(III) iodide, or titanium(III) sulfate, and especially preferably titanium(III) chloride. From the viewpoints of sufficient precipitation of tin and stability of the plating bath, the concentration of trivalent titanium as a reducing agent in the plating bath is preferably 0.1 g/L or more, more preferably 1 g/L or more, preferably 10 g/L or less, and more preferably 7 g/L or less.

[0022] Pyrophosphate salt as a complexing agent can be, for example, tetrapotassium pyrophosphate, tetrasodium pyrophosphate, or sodium dihydrogen pyrophosphate. From the viewpoint of stability in the plating bath, the concentration of pyrophosphoric acid as a complexing agent in the plating bath is preferably 20 g/L or more, more preferably 50 g/L or more, preferably 400 g/L or less, and more preferably 300 g/L or less.

[0023] The use of trivalent titanium as a reducing agent and the use of pyrophosphate salt as a complexing agent can reduce generation of bath decomposition in the plating bath. Accordingly, the thick surface layer 123 can be formed so that connection reliability of the stacked films 102 can be significantly increased. In the case of a plating bath having poor bath stability, a thick tin plating layer can be formed at a laboratory level, but is difficult to be formed by industrial production. On the other hand, the plating bath according to the present disclosure is highly stable, and thus, a thick tin plating layer with a thickness of 0.5 μm or more can be easily formed by industrial production.

[0024] The electroless tin plating bath according to this embodiment may include nitrogen-free organic thiol as an accelerating agent for accelerating precipitation of tin. Examples of the nitrogen-free organic thiol include 1-propanethiol, 1-botanethiol, 1,2-ethanedithiol, 1,2-propanedithiol, 1,4-butanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 2-aminoethanethiol, 3-mercapto-1,2-propanediol, 1,4-dimercapto-2,3-butanediol, 3-ethyl mercaptopropionate, benzenethiol, benzenetrithiol, 2,3-dichlorobenzenethiol, 2,4-dimethylbenzenethiol, 2-aminobenzenethiol, 2-naphtalenethiol, mercaptobenzoic acid, mercaptosuccinic acid, 3-mercaptopropionic acid, mercaptoacetic acid, mercaptosalicylic acid, 2-mercaptopropionic acid, 6-mercaptol-hexanol, 3-mercaptopropanol, 3-mercapto-1-hexanol, 3-mercaptoethanol, 2-sodium mercaptoethanesulfonate, 3-mercapto-1-sodium propanesulfonate, and 2,3-sodium dimercaptopropanesulfonate monohydrate. Nitrogen-free organic thiol can accelerate plating precipitation. The concentration of nitrogen-free organic thiol is preferably 0.1 g/L or more, more preferably 0.2 g/L or more, preferably 10 g/L or less, and more preferably 5 g/L or less.

[0025] From the viewpoint of accelerating plating precipitation to reduce a cycle time, the plating bath preferably includes an accelerating agent, but when trivalent titanium is used as a reducing agent and pyrophosphate salt is used as a complexing agent, a thick tin plating layer can be formed with stability even in the case of including no accelerating agent such as nitrogen-free organic thiol.

[0026] The electroless tin plating bath according to this embodiment can use, as an accelerating agent, sulfur oxoacid instead of nitrogen-free organic thiol or together with nitrogen-free organic thiol. Examples of sulfur oxoacid include dithionic acid, trithionic acid, tetrathionic acid, dithionous acid, and thiosulfuric acid. These materials may be in the state of salts. Examples of the salt include a sodium salt, a potassium salt, and an ammonium salt Specifically, the salt may be sodium tetrathionate, potassium tetrathionate, sodium trithionate, sodium dithionate, sodium dithionite, sodium thiosulfate, potassium thiosulfate, and ammonium thiosulfate. Sulfur oxoacid can accelerate plating precipitation. The concentration of sulfur oxoacid is preferably 0.1 mg/L or more, more preferably 1 mg/L or more, preferably 10 g/L or less, and more preferably 1 g/L or less.

[0027] The electroless tin plating solution according to this embodiment may include an antioxidant. The antioxidant may be, for example, one or more of catechol, pyrogallol, resorcinol, hydrochinone, ascorbic acid, and sorbitol. From the viewpoint of stability of the plating bath, the concentration of the antioxidant is preferably 0.1 g/L or more, preferably 50 g/L or less, and more preferably 10 g/L or less.

[0028] The pH of the electroless tin plating bath according to this embodiment is preferably 5.0 or more, more preferably 7.0 or more, preferably 10.0 or less, and more preferably 9.0 or less. To adjust the pH within an appropriate range, a pH adjuster can be used. Examples of the pH adjuster include inorganic acids such as phosphoric acid, hydrochloric acid, sulfuric acid, and nitric acid and organic acids such as formic acid, acetic acid, malic acid, and lactic acid. A compound having a buffer function such as a phosphoric acid buffer can also be used. Alternatively, a surfactant and a brightener may also be included, for example.

[0029] The bath temperature of the electroless tin plating bath in precipitating the surface layer 123 is preferably 40° C. or more, more preferably 60° C. or more, preferably 90° C. or less, and more preferably 80° C. or less. The plating time is preferably 10 minutes or more, preferably 180 minutes or less, and more preferably 60 minutes or less.

[0030] The electroless tin plating bath according to this embodiment can use titanium that has been oxidized from trivalent to tetravalent with the progress of plating and then reduced to trivalent again by an electroreduction process, for example. The reduction of tetravalent titanium to trivalent titanium can be performed by using, for example, an electroreduction tank 201 as illustrated in FIG. 2. The electroreduction tank 201 is divided into an anode chamber 211 and a cathode chamber 212 by a cation exchange membrane 213. An anode 215 of, for example, a titanium-platinum alloy is disposed in the anode chamber 211, and a cathode 216 of, for example, metal tin is disposed in the cathode chamber 212. An anode solution such as sulfuric acid is supplied to the anode chamber 211 and a plating solution is supplied to the cathode chamber 212 and a current is caused to flow so that tetravalent titanium is reduced to trivalent titanium on the cathode 216. As side reaction, tin ions are reduced to a metal and H+s reduced so that a hydrogen gas is generated.

[0031] The reduction from tetravalent titanium to trivalent titanium can be performed by a batch process, and may be performed in parallel with a plating process. In this case, it is sufficient that the plating solution circulates between the plating tank where the plating process is performed and the cathode chamber 212 of the electroreduction tank 201. In this case, a method in which a constant amount of the plating solution in the plating tank is fed to the electroreduction tank and is sent back to the plating tank after the electroreduction process, or a continuous circulation method in which the plating solution continuously circulates between the plating tank and the electroreduction tank, may be employed.

[0032] In the method for fabricating an electronic component according to this embodiment, a tin plating film with a thickness of 0.5 μm or more can be formed with stability on, for example, a printed wiring board and a wafer. Thus, even in a case where a thermal hysteresis is large in assembly, it is possible to avoid a situation where a tin plating film is alloyed with an underlying material and disappears, and connection reliability can be thereby significantly enhanced. As a result, the method according to this embodiment is useful as a method for fabricating an electronic component that requires connection reliability, for example.

EXAMPLES

[0033] The present disclosure will now be more specifically described with reference to examples. The following examples are illustrative examples and are not intended to limit the present disclosure.

<Connection Reliability Test>

[0034] Stacked films including a base material layer, a catalytic metal, and a surface layer were formed by a predetermined plating bath on a ball grid array (BGA) substrate (manufactured by C. Uyemura & Co., Ltd.). Solder balls (Sn-3.0 Ag-0.5 Cu-based solder balls with (φ) of 0.6 mm, manufactured by SENJU METAL INDUSTRY CO., LTD.) were joined to the BGA substrate with the stacked films, by using fluxes (529D-1, manufactured by SENJU METAL INDUSTRY CO., LTD.). The joint of solder balls was performed such that after the BGA substrate was subjected to a reflow process at a maximum temperature of 240° C., solder balls were mounted, and then, a reflow process was performed again at a maximum temperature of 240° C.

[0035] A ball pull test was conducted on the solder balls after the reflow process to obtain a solder fracture rate in a destructive mode. A result in which the solder fracture rate was 80% or more was evaluated as good (connected), and a result in which the solder fracture rate is less than 80% was evaluated as poor (disconnected).

<Electroless Tin Plating Bath>

[0036] As a plating bath A, a plating bath including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 5 g/L of titanium(III) chloride as a reducing agent, 200 g/L of potassium pyrophosphate as a complexing agent, 2 g/L of thiomalic acid as nitrogen-free organic thiol was prepared.

[0037] As a plating bath B, a plating bath including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 5 g/L of titanium(III) chloride as a reducing agent, 50 g/L of ethylenediaminetetraacetic acid (EDTA) as a complexing agent, and 2 g/L of thiomalic acid as nitrogen-free organic thiol was prepared.

[0038] As a plating bath C, a plating bath including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 0.5 g/L of sodium borohydride as a reducing agent, 200 g/L of potassium pyrophosphate as a complexing agent, and 2 g/L of thiomalic acid as nitrogen-free organic thiol was prepared.

[0039] As a plating bath D, a plating bath including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 0.5 g/L of sodium borohydride as a reducing agent, 50 g/L of ethylenediaminetetraacetic acid (EDTA) as a complexing agent, and 2 g/L of thiomalic acid as nitrogen-free organic thiol was prepared.

[0040] As a plating bath E, a plating path including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 5 g/L of titanium(III) chloride as a reducing agent, 200 g/L of potassium pyrophosphate as a complexing agent, and 100 mg/L of sodium thiosulfate as sulfur oxoacid was prepared.

[0041] As a plating bath F, a plating bath including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 5 g/L of titanium(III) chloride as a reducing agent, 200 g/L of potassium pyrophosphate as a complexing agent, and 1 g/L of sodium dithionite as sulfur oxoacid was prepared.

[0042] As a plating bath G, a plating bath including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 5 g/L of titanium(III) chloride as a reducing agent, 200 g/L of potassium pyrophosphate as a complexing agent, and 1 g/L of potassium tetrathionate as sulfur oxoacid was prepared.

[0043] As a plating bath H, a plating path including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 5 g/L of titanium(III) chloride as a reducing agent, 50 g/L of ethylenediaminetetraacetic acid (EDTA) as a complexing agent, and 100 mg/L of sodium thiosulfate as sulfur oxoacid was prepared.

[0044] As a plating bath I, a plating path including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 0.5 g/L of sodium borohydride as a reducing agent, 200 g/L of potassium pyrophosphate as a complexing agent, and 100 mg/L of sodium thiosulfate as sulfur oxoacid was prepared.

[0045] As a plating bath J, a plating path including tin(II) chloride in a tin concentration of 10 g/L as a tin compound, 0.5 g/L of sodium borohydride as a reducing agent, 50 g/L of ethylenediaminetetraacetic acid (EDTA) as a complexing agent, and 100 mg/L of sodium thiosulfate as sulfur oxoacid was prepared.

[0046] Tables 1 and 2 collectively show compositions of prepared electroless tin plating baths.

TABLE-US-00001 TABLE 1 Electroless Sn Plating Bath Plating Bath Plating Bath Plating Bath Plating Bath A B C D Reducing trivalent trivalent sodium sodium Agent titanium titanium borahydride borohydride 5.0 (g/L) 5.0 (g/L) 0.5 (g/L) 0.5 (g/L) Complexing pyrophosphate EDTA pyrophosphate EDTA Agent salt 50 (g/L) salt 50 (g/L) 200 (g/L) 200 (g/L) tin(II) 10 (g/L) 10 (g/L) 10 (g/L) 10 (g/L) chloride (Sn compound) thiomalic  2 (g/L)  2 (g/L)  2 (g/L)  2 (g/L) acid (nitrogen- free organic thiol)

TABLE-US-00002 TABLE 2 Electroless Sn Plating Bath Plating Plating Plating Plating Plating Plating Bath E Bath F Bath G Bath H Bath I Bath J Reducing trivalent trivalent trivalent trivalent sodium sodium Agent titanium titanium titanium titanium borohydride borohydride 5.0 (g/L) 5.0 (g/L) 5.0 (g/L) 5.0 (g/L) 0.5 (g/L) 0.5 (g/L) Complexing pyrophos- pyrophos- pyrophos- EDTA pyrophos- EDTA Agent phate salt phate salt phate salt 50 (g/L) phate salt 50 (g/L) 200 (g/L) 200 (g/L) 200 (g/L) 200 (g/L) tin(II) 10 (g/L) 10 (g/L) 10 (g/L) 10 (g/L) 10 (g/L) 10 (g/L) chloride (Sn compound) sulfur sodium dithionous potassium sodium sodium sodium oxoacid thiosulfate acid tetrathio- thiosulfate thiosulfate thiosulfate 100 (mg/L) 1 (g/L) nate 100 (mg/L) 100 (mg/L) 100 (mg/L) 1 (g/L)

<Bath Stability>

[0047] When a prepared electroless tin plating bath is left for one hour at a plating temperature of 70° C., it is determined whether precipitation (beaker precipitation) occurs or not A result in which precipitation does not occur is represented as “good” and a result in which precipitation occurs is represented as “poor.”

Example 1

[0048] As a pretreatment, degreasing, softetching, and pickling were performed on the surface of a copper underlying layer (base material layer). A palladium catalyst was applied onto the underlying layer subjected to the pretreatment, and a base material layer with a thickness of 2.0 μm was formed by an electroless nickel plating bath (electroless Ni plating solution NPR-4, manufactured by C. Uyemura & Co., Ltd.). After silver (Ag) was applied as a catalytic metal to the base material layer, a surface layer with a thickness of 0.5 μm was formed by using the electroless plating bath A. The plating time was 15 minutes, and the plating temperature was 70° C. The thickness was measured by a fluorescent X-ray coating thickness gauge (FT150, manufactured by Hitachi High-Tech Science Corporation).

[0049] In a case where the plating bath was allowed to stand for one hour at a plating temperature of 70° C., bath decomposition did not cause beaker precipitation, and the plating bath was stable. Under the same conditions, a film was formed on a BGA substrate and a connection reliability test was conducted. The result of the test was good.

Example 2

[0050] Example 2 is similar to Example 1 except that the catalytic metal was palladium (Pd). The connection reliability test was good.

Example 3

[0051] Example 3 is similar to Example 1 except that the catalytic metal was gold (Au). The connection reliability test was good.

Example 4

[0052] As a pretreatment, degreasing, pickling, primary zincate, pickling, and secondary zincate were performed on the surface of an underlying layer of an aluminium-copper alloy. A palladium catalyst was applied to the pretreated underlying layer, and a base material layer with a thickness of 2.0 μm was formed by using an electroless nickel plating bath (electroless Ni plating solution NPR-4, manufactured by C. Uyemura & Co., Ltd.). Silver (Ag) was applied as a catalytic metal to the base material layer, and a surface layer having a 0.5 μm was formed by using the electroless plating bath A. The plating time was 15 minutes, and the plating temperature was 70° C.

[0053] Under the same conditions, a film was formed on a BGA substrate, and a connection reliability test was conducted. The result of the test was good.

Example 5

[0054] Example 5 is similar to Example 4 except that the catalytic metal was palladium (Pd). The result of the connection reliability test was good.

Example 6

[0055] Example 6 is similar to Example 4 except that the catalytic metal was gold (Au). The result of the connection reliability test was good.

Comparative Example 1

[0056] Comparative Example 1 is similar to Example 1 except that no catalytic metal was applied to the base material layer. Tin precipitation did not occur, and no surface layer was formed. A connection reliability test was conducted without formation of a surface layer. The result of the test was poor.

Comparative Example 2

[0057] Comparative Example 2 is similar to Example 4 except that no catalytic metal was applied to the base material layer. Tin precipitation did not occur, and no surface layer was formed. A connection reliability test was conducted without formation of a surface layer. The result of the test was poor.

Comparative Example 3

[0058] Comparative Example 3 is similar to Example 1 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 4

[0059] Comparative Example 4 is similar to Example 2 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 5

[0060] Comparative Example 5 is similar to Example 3 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 6

[0061] Comparative Example 6 is similar to Example 4 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 7

[0062] Comparative Example 7 is similar to Example 5 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 8

[0063] Comparative Example 8 is similar to Example 6 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 9

[0064] Comparative Example 9 is similar to Example 1 except that the electroless tin plating bath B was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. After the plating bath was left in one hour at the plating temperature, beaker precipitation occurred and the plating bath was unstable. The result of the connection reliability test was poor.

Comparative Example 10

[0065] Comparative Example 10 is similar to Example 2 except that the electroless tin plating bath B was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 11

[0066] Comparative Example 11 is similar to Example 3 except that the electroless tin plating bath B was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 12

[0067] Comparative Example 12 is similar to Example 4 except that the electroless tin plating bath B was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 13

[0068] Comparative Example 13 is similar to Example 5 except that the electroless tin plating bath B was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 14

[0069] Comparative Example 13 is similar to Example 6 except that the electroless tin plating bath B was used, the plating time was 6 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 15

[0070] Comparative Example 15 is similar to Example 9 except that the plating time was 25 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.5 μm. The result of the connection reliability test was good, but repetitive use was difficult because of unstable plating bath.

Comparative Example 16

[0071] Comparative Example 16 is similar to Example 1 except that the electroless tin plating bath C was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. After the plating bath was left in one hour at the plating temperature, beaker precipitation occurred and the plating bath was unstable. The result of the connection reliability test was poor.

Comparative Example 17

[0072] Comparative Example 17 is similar to Example 2 except that the electroless tin plating bath C was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 18

[0073] Comparative Example 18 is similar to Example 3 except that the electroless tin plating bath C was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 19

[0074] Comparative Example 19 is similar to Example 4 except that the electroless tin plating bath C was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 20

[0075] Comparative Example 20 is similar to Example 5 except that the electroless tin plating bath C was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 21

[0076] Comparative Example 21 is similar to Example 6 except that the electroless tin plating bath C was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 22

[0077] Comparative Example 22 is similar to Example 17 except that the plating time was 25 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.5 μm. The result of the connection reliability test was good, but repetitive use was difficult because of unstable plating bath.

Comparative Example 23

[0078] Comparative Example 23 is similar to Example 1 except that the electroless tin plating bath D was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. After the plating bath was left in one hour at the plating temperature, beaker precipitation occurred and the plating bath was unstable. The result of the connection reliability test was poor.

Comparative Example 24

[0079] Comparative Example 24 is similar to Example 2 except that the electroless tin plating bath D was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 25

[0080] Comparative Example 25 is similar to Example 3 except that the electroless tin plating bath D was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 26

[0081] Comparative Example 26 is similar to Example 4 except that the electroless tin plating bath D was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 27

[0082] Comparative Example 27 is similar to Example 5 except that the electroless tin plating bath D was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 28

[0083] Comparative Example 28 is similar to Example 6 except that the electroless tin plating bath D was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 29

[0084] Comparative Example 29 is similar to Example 25 except that the plating time was 25 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.5 μm. The result of the connection reliability test was good, but repetitive use was difficult because of unstable plating bath.

[0085] Tables 3 through 7 collectively show results of the examples and the comparative examples.

TABLE-US-00003 TABLE 3 Examples 1 2 3 4 5 6 Base Material Cu Qu Cu Al—Cu Al—Cu Al—Cu Layer Catalytic Ag Pd Au Ag Pd Au Metal Sn Plating A A A A A A Bath Surface Layer 0.5 0.5 0.5 0.5 0.5 0.5 Thickness (μm) Stability good good good good good good Connection good good good good good good Reliability

TABLE-US-00004 TABLE 4 Comparative Examples 1 2 3 4 5 6 7 8 Bass Material Cu Al—Cu Cu Cu C Al—Cu Al—Cu Al—Cu Layer Catalytic Metal — — Ag Pd Au Ag Pd Au Sn Plating Bath A A A A A A A A Surface Layer unprecipitated unprecipitated 04 0.4 0.4 0.4 0.4 0.4 Thickness (μm) Stability good good good good good good good good Connection poor poor poor poor poor poor poor poor Reliability

TABLE-US-00005 TABLE 5 Comparative Examples 8 10 11 12 13 14 15 Bass Material Cu Cu Ou Al—Cu Al—Cu Al—Cu Cu Layer Catalytic Ag Pd Au As Pd Au Ag Metal Sn Plating B B B B B B B Bath Surface Layer 0.1 0.1 0.1 0.1 01 0.1 0.5 Thickness (μm) Stability poor poor poor poor poor poor poor Connection poor poor poor poor poor poor good Reliability

TABLE-US-00006 TABLE 6 Comparative Examples 16 17 18 19 20 21 22 Base Material Cu Cu Cu Al—Cu Al—Cu Al—Cu Cu Layer Catalytic Ag Pd Au Ag Pd Au Pd Metal Sn Plating C C C C C C C Bath Surface Layer 0.1 0.1 0.1 0.1 0.1 0.1 0.5 Thickness (μm) Stability poor poor poor poor poor poor poor Connection poor poor poor poor poor poor good Reliability

TABLE-US-00007 TABLE 7 Comparative Examples 23 24 25 26 27 28 29 Base Material Cu Cu Cu Al—Cu Al—Cu Al—Cu Cu Laver Catalytic Ag Pd Au Ag Pd Au Au Metal Sn Plating D D D D D D D Bath Surface Layer 0.1 0.1 0.1 0.1 0.1 0.1 0.5 Thickness (μm) Stability poor poor poor poor poor poor poor Connection poor poor poor poor poor poor good Reliability

Example 7

[0086] In a manner similar to Example 1, the base material layer was made of Cu, the catalytic metal applied to the base material layer was Ag, and plating was performed for 15 minutes at 70° C. by using the electroless tin plating bath E so that a surface layer with a thickness of 0.5 μm was formed. In a case where the plating bath was allowed to stand for one hour at a plating temperature of 70° C., bath decomposition did not cause beaker precipitation, and the plating bath was stable. The result of the connection reliability test was good.

Example 8

[0087] Example 8 is similar to Example 7 except that the catalytic metal was palladium (Pd). The result of the connection reliability test was good.

Example 9

[0088] Example 9 is similar to Example 7 except that the catalytic metal was gold (Au). The result of the connection reliability test was good.

Example 10

[0089] In a manner similar to Example 4, the base material layer was made of Al—Cu, the catalytic metal applied to the base material layer was Ag, and plating was performed for 15 minutes at 70° C. by using the electroless tin plating bath E so that a surface layer with a thickness of 0.5 μm was formed. The result of the connection reliability test was good.

Example 11

[0090] Example 11 is similar to Example 10 except that the catalytic metal was palladium (Pd). The result of the connection reliability test was good.

Example 12

[0091] Example 12 is similar to Example 10 except that the catalytic metal was gold (Au). The result of the connection reliability test was good.

Example 13

[0092] Example 13 is similar to Example 7 except that the electroless tin plating bath F was used. In a case where the plating bath was allowed to stand for one hour at a plating temperature of 70° C., bath decomposition did not cause beaker precipitation, and the plating bath was stable. The result of the connection reliability test was good.

Example 14

[0093] Example 14 is similar to Example 13 except that the catalytic metal was palladium (Pd). The result of the connection reliability test was good.

Example 15

[0094] Example 15 is similar to Example 13 except that the catalytic metal was gold (Au). The result of the connection reliability test was good.

Example 16

[0095] Example 16 is similar to Example 10 except that the electroless tin plating bath F was used. The result of the connection reliability test was good.

Example 17

[0096] Example 17 is similar to Example 16 except that the catalytic metal was palladium (Pd). The result of the connection reliability test was good.

Example 18

[0097] Example 18 is similar to Example 16 except that the catalytic metal was gold (Au). The result of the connection reliability test was good.

Example 19

[0098] Example 19 is similar to Example 7 except that the electroless tin plating bath G was used. In a case where the plating bath was allowed to stand for one hour at a plating temperature of 70° C., bath decomposition did not cause beaker precipitation, and the plating bath was stable. The result of the connection reliability test was good.

Example 20

[0099] Example 20 is similar to Example 19 except that the catalytic metal was palladium (Pd). The result of the connection reliability test was good.

Example 21

[0100] Example 21 is similar to Example 19 except that the catalytic metal was gold (Au). The result of the connection reliability test was good.

Example 22

[0101] Example 22 is similar to Example 10 except that the electroless tin plating bath G was used. The result of the connection reliability test was good.

Example 23

[0102] Example 23 is similar to Example 22 except that the catalytic metal was palladium (Pd). The result of the connection reliability test was good.

Example 24

[0103] Example 24 is similar to Example 22 except that the catalytic metal was gold (Au). The result of the connection reliability test was good.

Comparative Example 30

[0104] Comparative Example 30 is similar to Example 7 except that no catalytic metal was applied to the surface layer. Tin precipitation did not occur, and no surface layer was formed. A connection reliability test was conducted without formation of a surface layer. The result of the test was poor.

Comparative Example 31

[0105] Comparative Example 31 is similar to Example 10 except that no catalytic metal was applied to the surface layer. Tin precipitation did not occur, and no surface layer was formed. A connection reliability test was conducted without formation of a surface layer. The result of the test was poor.

Comparative Example 32

[0106] Comparative Example 32 is similar to Example 7 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 33

[0107] Comparative Example 33 is similar to Example 8 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 34

[0108] Comparative Example 34 is similar to Example 9 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 35

[0109] Comparative Example 35 is similar to Example 10 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 36

[0110] Comparative Example 36 is similar to Example 11 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 37

[0111] Comparative Example 37 is similar to Example 12 except that the plating time was 12 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.4 μm. The result of the connection reliability test was poor.

Comparative Example 38

[0112] Comparative Example 38 is similar to Example 7 except that the electroless tin plating bath H was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. After the plating bath was left in one hour at a plating temperature of 70° C., beaker precipitation occurred and the plating bath was unstable. The result of the connection reliability test was poor.

Comparative Example 39

[0113] Comparative Example 39 is similar to Example 8 except that the electroless tin plating bath H was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 40

[0114] Comparative Example 40 is similar to Example 9 except that the electroless tin plating bath H was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 41

[0115] Comparative Example 41 is similar to Example 10 except that the electroless tin plating bath H was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 42

[0116] Comparative Example 42 is similar to Example 11 except that the electroless tin plating bath H was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 43

[0117] Comparative Example 43 is similar to Example 12 except that the electroless tin plating bath H was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 44

[0118] Comparative Example 44 is similar to Example 38 except that the plating time was 25 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.5 μm. The result of the connection reliability test was good, but repetitive use was difficult because of unstable plating bath.

Comparative Example 45

[0119] Comparative Example 45 is similar to Example 7 except that the electroless tin plating bath I was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. After the plating bath was left in one hour at a plating temperature of 70° C., beaker precipitation occurred and the plating bath was unstable. The result of the connection reliability test was poor.

Comparative Example 46

[0120] Comparative Example 46 is similar to Example 8 except that the electroless tin plating bath I was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 47

[0121] Comparative Example 47 is similar to Example 9 except that the electroless tin plating bath I was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 48

[0122] Comparative Example 48 is similar to Example 10 except that the electroless tin plating bath I was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 49

[0123] Comparative Example 49 is similar to Example 11 except that the electroless tin plating bath I was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 50

[0124] Comparative Example 50 is similar to Example 12 except that the electroless tin plating bath I was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 51

[0125] Comparative Example 51 is similar to Example 46 except that the plating time was 25 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.5 μm. The result of the connection reliability test was good, but repetitive use was difficult because of unstable plating bath.

Comparative Example 52

[0126] Comparative Example 52 is similar to Example 7 except that the electroless tin plating bath J was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. After the plating bath was left in one hour at a plating temperature of 70° C., beaker precipitation occurred and the plating bath was unstable. The result of the connection reliability test was poor.

Comparative Example 53

[0127] Comparative Example 53 is similar to Example 8 except that the electroless tin plating bath J was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 54

[0128] Comparative Example 54 is similar to Example 9 except that the electroless tin plating bath J was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 55

[0129] Comparative Example 55 is similar to Example 10 except that the electroless tin plating bath J was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 56

[0130] Comparative Example 56 is similar to Example 11 except that the electroless tin plating bath J was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 57

[0131] Comparative Example 57 is similar to Example 12 except that the electroless tin plating bath J was used, the plating time was 5 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.1 μm. The result of the connection reliability test was poor.

Comparative Example 58

[0132] Comparative Example 58 is similar to Example 54 except that the plating time was 25 minutes, the plating temperature was 70° C., and the thickness of the surface layer was 0.5 μm. The result of the connection reliability test was good, but repetitive use was difficult because of unstable plating bath.

[0133] Tables 8 through 14 collectively show results of the examples and the comparative examples.

TABLE-US-00008 TABLE 8 Examples 7 8 9 10 11 12 Base Material Cu Cu Cu Al—Cu Al—Cu Al—Cu Layer Catalytic Ag Pd Au Ag Pd Au Metal Sn Plating E E E E E E Bath Surface Layer 0.5 0.5 0.5 0.5 0.5 0.5 Thickness (μm) Stability good good good good good good Connection good good good good good good Reliability

TABLE-US-00009 TABLE 9 Examples 13 14 15 16 17 18 Base Material Cu Cu Cu Al—Cu Al—Cu Al—Cu Layer Catalytic Ag Pd Au Ag Pd Au Metal Sn Plating F F F F F F Bath Surface Layer 0.5 0.5 0.5 0.5 0.5 0.5 Thickness (μm) Stability good good good good good good Connection good good good good good good Reliability

TABLE-US-00010 TABLE 10 Examples 19 20 21 22 23 24 Base Material Cu Cu Cu Al—Cu Al—Cu Al—Cu Layer Catalytic Ag Pd Au Ag Pd Au Metal Sn Plating G G G G G G Bath Surface Layer 0.5 0.5 0.5 0.5 0.5 0.5 Thickness (μm) Stability good goug gsw good good good Connection good good good good good good Reliability

TABLE-US-00011 TABLE 11 Comparative Examples 30 31 32 33 34 35 38 37 Base Material Cu Al—Cu Cu Cu Cu Al—Cu Al—Cu Al—Cu Layer Catalytic Metal — — Ag Pd Au Ag Pd Au Sn Plating Bath E E E E E E E E Surface Layer unprecipitated unprecipitated 0.4 0.4 0.4 0.4 0.4 0.4 Thickness (μm) Stability good good good good good good good good Connection poor poor poor poor poor poor poor poor Reliability

TABLE-US-00012 TABLE 12 Comparative Examples 38 39 40 41 42 43 44 Base Material Cu Cu Cu Al—Cu Al—Cu Al—Cu Cu Layer Catalytic Ag Pd Au Ag Pd Au Ag Metal Sn Plating H H H H H H H Bath Surface Layer 0.1 0.1 0.1 0.1 0.1 0.1 0.5 Thickness (μm) Stability poor poor poor poor poor poor poor Connection poor poor poor poor poor poor good Reliability

TABLE-US-00013 TABLE 13 Comparative Examples 45 46 47 48 48 50 51 Base Material Cu Cu Cu Al—Cu Al—Cu Al—Cu Cu Layer Catalytic Ag Pd Au Ag Pd Au Pd Sn Plating I I I I I I I Bath Surface Layer 0.1 0.1 0.1 0.1 0.1 0.1 0.5 Thickness (μm) Stability poor poor poor poor poor poor poor Connection poor poor poor poor poor poor good Reliability

TABLE-US-00014 TABLE 14 Comparative Examples 52 53 54 55 56 57 58 Base Material Cu Cu Cu Al—Cu Al—Cu Al—Cu Cu Layer Catalytic Ag Pd Au Ag Pd Au Au Metal Sn Plating J J J J J J J Bath Surface Layer 0.1 0.1 0.1 0.1 0.1 0.1 0.5 Thickness (μm) Stability poor poor poor poor poor poor poor Connection poor poor poor poor poor poor good Reliability

[0134] A method for fabricating an electronic component according to the present disclosure enables stable fabrication of a sufficiently thick Sn plating film with high connection reliability, and thus, is useful as a method for fabricating an electronic component, for example.